Preparation Of Reversible Light-responsive Polyester Micelles Via Azide-alkyne Click Chemistry

Poly(a-hydroxy acids)(PAHAs),such as poly(lactic acid)(PLA),poly(glycolic acid),are widely used in controlled drug release,drug delivery and tissue engineering because of their excellent biocompatibility and biodegradability.Recently,ring opening polymerization(ROP)of O-Carboxyanhydrides(OCAs),a class of five member ring compounds,has emerged as an efficient method to prepare side-chain functionalized PAHAs.In this thesis,we designed and synthesized an OCA monomer with alkynyl functional group.ROP of the new monomer using hydriphiphilic macroinitator give an amphiphilic block copolymer.Then,a series of photo-responsive amphiphilic block copolymer were fabricated via azide-alkyne click chemistry with diverse chemical architectures.The details are given in the following parts:Firstly,we synthesized a Tyr(alkynyl)-OCA monomer using tyrosine as raw material.After ROP of tyr(alkynyl)-OCA which poly(ethylene glycol)(mPEG)as macroinitiator at monomer/initiator(M/I)ratios of 25,amphiphilic diblock copolymer mPEG-b-poly(tyr(alkynyl)-OCA)25 was obtained.This amphiphilic block copolymer can self-assemble to spherical micelles with an average diameter of about 200 nm and a critical micelle concentration of 0.0138 mg/mL by fluorescence emission spectrum,dynamic light scattering(DLS),and transmission electron microscope(TEM).Secondly,we used azide-alkyne "click chemistry" methods to modify the obtained amphiphilic block copolymers with azobenzene,coumarin and spiropyrane derivatives which contain azide functional groups.Then,we used SEM,DLS and fluorescence emission spectrum to characterize the the spherical morphology of copolymer micelles,the CMCs of the micelles are reduced,the particle diameters become larger.We also explored the effect of the photochemical transformation of organic functional molecules on the self-assemble and disassemble of amphiphilic block copolymer.The results showed that under UV,in spherical micelles nucleus the change of cis-trans isomerizationtrans isomerization dipole moment can cause disintegration of the micelles and cause changes in the morphology of the micelles;the backlit dimerization of coumarin can improve the stability of micelles;the change of reversible hydrophobiccan can cause the disassemble and reassemble of micelles.